I think, first, you must going in with the knowledge that it will be unbelievably crowded. Like, you can barely move or walk from place to place crowded. We went to MK on Dec. 29, 2015. Got there just after RD (tried to get there at RD, but the traffic was so bad, and we were on Disney transportation BTW, that it took us about 45 minutes to get from BWI to MK). By 10 am it was wall-to-wall people. As others have mentioned, we were able to do our 3 FP+ and that was about it. We did stand in line for Peoplemover (about 40 minutes) and my DS got his face painted in Tomorrowland because it was literally the only place we could find a seat and no crowd.
Are you planning on RD until park close? If so, I would just expect to be in big crowds waiting in long lines the entire time.
What I would do, personally (if you aren't going to attempt heavy park touring) is arrive about 1 1/2 hours before the parade, find a spot, schedule your 3 FP+ for after the parade, get a TS ADR somewhere in MK (QS locations will be completely mobbed), then find your spot for the fireworks. I would also consider splurging and reserving the MK fireworks dessert party with Plaza viewing if you can swing the cost. It's a great way to see the fireworks without a huge crowd.